-LRB- CNN -RRB- -- Dozens of protesters were injured Sunday by Yemeni security forces as thousands packed into anti-government demonstrations , witnesses and medical personnel said .

Witnesses said some others were arrested , but officials said they were released within hours .

In Sanaa 's Change Square , Yemeni security forces shot live ammunition at protesters , injuring 11 , witnesses and field medical teams said .

All 11 had gunshot wounds , witnesses said . Two of the injured are in serious condition , medical staff at the square said .

`` We were being shot at directly , '' said protester Abdullah Kulaibi . `` Security forces were trying to kill us and not disperse us . ''

Yemeni officials have repeatedly denied accusations of targeting peaceful protesters .

Witnesses said at least 20 protesters were arrested Sunday . A security official said they were released about two hours later . The official asked not to be identified , as he is not authorized to speak to the media . Field medical teams in Sanaa said some of the releases came because the detainees needed medical treatment after inhaling tear gas . One medical team member , Osama Qurashi , said those who were seriously impaired were taken to nearby hospitals , while the rest were taken to a field medical hospital set up in Change Square .

For weeks , demonstrators have taken to the streets calling for President Ali Abdullah Saleh to step down .

In Dhammar province on Sunday , more than 45 anti-Saleh protesters were injured when security forces sprayed tear gas to disperse them , eyewitnesses said .

Security forces also attacked some demonstrators with batons , injuring at least five , according to the medical staff at Change Square in Dhammar .

The latest marches against Saleh 's regime came as the opposition Joint Meeting Parties sent a delegation to Saudi Arabia , where mediators are hoping to broker an agreement . Opposition officials told CNN their delegation was traveling to hear the ideas of the mediators , not to make an offer to the Yemeni government .

Some protesters in Yemen said whatever transpires at those talks wo n't change their stance . `` Any negotiations that does not force Saleh to leave office will be rejected , '' said Shaef Saboor , a human rights activist in Sanaa .

Sanaa 's main roads were flooded with crowds estimated by eyewitnesses as being in the tens of thousands pushing for a revolution -- most of them women , according to eyewitnesses . `` Every day the number will grow . Today more females than males are protesting , thanks to Saleh 's attack on women protesters , '' said Ameera Abdul Jabbar , a female activist in Sanaa .

In a speech given Friday , Saleh said women who were protesting were violating Yemeni cultural norms that prohibit women mixing with men who are not direct relatives . His comments angered many activists .

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11 protesters have gunshot wounds , witnesses said

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Witnesses : More than 45 protesters injured when security forces sprayed tear gas

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The Yemeni government has denied targeting peaceful protesters